1. Field
The invention is in the field of machines and methods which utilize a rotating cutter that engages a slowly rotating used motor vehicle tire to remove tread material from the tire for recycling of such tread material in preparation for tire disposal or retreading.
2. State of the Art
Various types of vehicle tire cutting or shredding machines and methods for use thereof have been developed to remove chunks of tread material and tire core (i.e. cords) from used vehicle tires or for complete shredding thereof for disposal or recycling. Reference is made to my U.S. Pat. Nos. 5,299,748 and 5,590,838 which describe several such prior art shredding machines that typically completely shred used tires into relatively large pieces of about four inches long by four inches wide by one-half inch thick, requiring subsequent processing thereof prior to recycling for separation of the cloth and metal of the tire cords and tire bead components from the recyclable tread material. Shearing of such tires also makes transport thereof easier, requiring less space to transport. Such shearing-type machines, however, are only economically feasible to shear tires of up to the size of standard automobile tires. Other types of machines have been used to remove tread material from used tires, including those using a narrow, cylindrical wire cutting brush having a hub and radially-extending wire bristles. Such a brush is about one and one-half to three inches wide by about ten to twenty inches in diameter, and is reciprocated during use so as to reach the full width of the tire tread material. Applicant is not aware of any prior art brushes comprising a plurality of this type of brush formed by placing side-by-side multiple narrow brushes so as to form a wider brush.
In such U.S. Patents I disclose and claim a machine and method for cutting tread material from the outer, ground-contacting portion of large, used, off-road industrial vehicle tires and for completely disintegrating tires by cutting, including the sidewalls thereof. A tire to be cut is mounted in an upright position on a motor driven, rotating, tire holder assembly of the machine, which expands to grip the tire beads and rotates the tire. The tire holder assembly is held on the supporting structure by means of an arbor thereof which extends through such tire holder assembly. The tire holder assembly is rotatably chain driven by a motor attached to the supporting structure. A powered, elongate, rotating, cutting blade assembly, having a series of staggered, chisel-type, cutting blades, is rotatably mounted on a rolling mounting structure in a horizontal position laterally of the mounted tire. The cutting blade assembly is rotatably driven at a higher speed than the tire holder assembly by a motor attached to the mounting structure. As the tire is rotated, the cutting blades remove relatively large pieces of tire similar to the shredding machines. These pieces are ready for direct disposal, such as in a landfill, or for further processing for recycling, such as by liquid nitrogen freezing, followed by crushing into crumb rubber, and sorting out of the recyclable tread material from the cloth and metal. While my prior machine and other prior art shredding machines are capable of cutting whole tires into pieces, the pieces are not readily recyclable, and the machines are not well suited or capable of removing only the tread material for recycling or to prepare tires for adding new tread material thereto (i.e. retreading). Also, such machines require the tires to be brought to the location of the machine, which is more costly than if the machine could be brought to the location of the tires.
When removing tread material for recycling, or preparing tires for retreading, using my prior machine and method, only the tread material on the outer, ground-contacting portion of the tire is removed, this by making one or more rough cuts with the cutting blades. Such rough cuts are stopped short of the tire cords and sidewalls. Additional tread material can be removed by replacing the cutting blades with an elongate, rotatable, cylindrical cutting brush having straight, radially-extending wire bristles for removing additional tread material without damaging the tire cords. The tread material removed by such brush is in the form of "shards", which are about one-eighth to one-quarter inch wide, of varying thickness, and up to several inches long, which contain very little cord material. The brush prepares the outer, ground-contacting portion of the tire for retreading by producing a smoother, slightly roughened surface compared to the blades. However, tread material on the sidewalls cannot be reached by the cutting blades nor by the brush without damaging the tire cords, because the brush and the tire cannot pivot relative to one another such that the cutter and brush can engage the tread material on the sidewalls. Likewise, applicant is not aware of any prior art machines in which the cutter or the tire supporting structure can be pivoted so as to facilitate cutting the tread material from the tire sidewalls.
The removal of tread material using the cutting brush is a relatively slow process compared to using the cutting blades, since the brush removes only "shards" from the tire and since this process must be done at a relatively slow brush speed of about 450 to 900 revolutions per minute (RPM) due to the frictional heat build-up in the brush as the bristles contact the tread material. As the frictional heat builds, the tread material softens, and if the temperature reaches the melting point of the tread material, the tread material melts onto the brush bristles and no longer comes off of the tire as solid chips, thus ruining the brush, and prohibiting further tread material removal from the tire until the brush and tread material are cooled to a temperature below the melting point of the tread material. One such method of preventing the excessive build-up of heat is by spraying liquid nitrogen onto the tread material ahead of the brush so as to freeze the tread material. This method also allows the brush to be run at higher RPM's for quicker tread material removal. However, such a process using liquid nitrogen or other liquid gas is more costly due to the cost of the gas and typically requires more elaborate equipment including an insulating hood to cover the tire.
Rotatable brushes having radially extending bristles are known in various arts and have been used in various machines including floor sweepers, paint removal devices, and in the machine of my prior-mentioned patents. However, the bristles on such brushes are generally straight members made of metal, or plastic, extending radially from a hub. More recently, rotating brushes having radially extending bristles which are crimped along their length and twisted, which crimps can engage or abut adjacent bristles so as to maintain the bristle ends spaced apart have been developed for use in various applications wherein a more even bristle distribution is desired at the outer surface of the rotating brush to produce a more even cut. While such brushes having radial bristles are well known, modifications thereof for the purposes of the present invention appear to be new. In particular, applicant is not aware of any brushes having such twisted, crimped bristles which are used for cooling purposes due to an increased air space and flow between the bristles.